Those skilled in the refrigeration art will understand and appreciate the seasonal climatic influence on large commercial and industrial refrigeration systems of the type disclosed. The primary function of such systems is to provide efficient year-round refrigeration of the respective fixtures or units cooled by the system evaporators, and the most efficient refrigeration is obtained by delivering subcooled liquid refrigerant to the expansion valves therefor. Subcooling is inherently obtained during winter and intermediate seasons by using conventional condenser flooding and/or multi-pass condensers to control or maintain the minimum compressor head pressure requisite for total system operation, as taught by U.S. Pat. No. 3,358,469. Such subcooling can result in substantial energy or power savings unless it has to be obtained by offsetting power usage through the use of conventional mechanical subcooler units in the liquid line to the expansion valves to prevent, flash gas due to liquid line pressure reduction during gas defrosting, as taught by U.S. Pat. No. 3,150,490. Thus, the advantages of liquid refrigerant subcooling in efficient operation of system compressors and evaporators and the potential power savings thereby achieved are well known. However, heretofore the installation of conventional mechanical subcoolers for use during summer operations has remained the primary solution to efficient system refrigeration during hot weather.
The use of heat reclamation is also well understood and can result in substantial energy or power savings during winter and intermediate seasons depending upon the relative costs of electrical compressor power and heating fuel. If the compressor head pressure is increased there will be a higher heat reclamation potential, but at a higher power consumption by the compressors, as discussed in U.S. Pat. No. 4,522,037.